The synthesis of anisotropic nanocrystals, such as nanorods, nanowires, nanotubes, and nanodisks, is of great importance to applications ranging from chemical and biological sensing, separation, and catalysis, to lasers and LEDs. The formation of anisotropic nanostructures has been achieved by shape control in the crystallization process that includes the steps of nucleation and growth. In colloidal synthesis, parameters including ligands, precursors and reaction temperature are chosen to affect the kinetics and thermodynamics in the nucleation and growth of nanocrystals to achieve shape control. In convention synthesis methods, precursor injection is used throughout the growth process. Such processes have led to the synthesis of a variety of nanocrystals including nanorods and nanowires, as well as PbS nanostars, Ag cubes and tetrapod-shaped CdTe NCs. However, precursor injection adds to process complication, introduces variability in results obtainable, and makes production scale-up difficult.
Nanocrystals may be used as the building blocks for close-packed nanocrystal solids. Under controlled conditions, provided the nanocrystals are highly uniform in size, the organic monolayer coordinating each nanocrystal surface enables uniform nanocrystal samples to self-assemble into nanocrystal superlattices.